lsof命令

第一个进程

[root@LinuxOparation ~]# cd /proc/$$/fd
[root@LinuxOparation fd]# pwd
/proc/32629/fd
[root@LinuxOparation fd]# exec 8< /root/newDir/newfile.txt 
[root@LinuxOparation fd]# read firstline <& 8
[root@LinuxOparation fd]# echo $firstline
aa
[root@LinuxOparation fd]# read firstline <& 8
[root@LinuxOparation fd]# read firstline <& 8
[root@LinuxOparation fd]# echo $firstline
dasda
[root@LinuxOparation fd]# lsof -op $$
COMMAND   PID USER   FD   TYPE DEVICE OFFSET    NODE NAME
bash    32629 root  cwd    DIR    0,3        2216432 /proc/32629/fd
bash    32629 root  rtd    DIR  253,1              2 /
bash    32629 root  txt    REG  253,1         657640 /usr/bin/bash
bash    32629 root  mem    REG  253,1         666054 /usr/lib/locale/locale-archive
bash    32629 root  mem    REG  253,1         663465 /usr/lib64/libnss_files-2.17.so
bash    32629 root  mem    REG  253,1         657568 /usr/lib64/libc-2.17.so
bash    32629 root  mem    REG  253,1         663461 /usr/lib64/libdl-2.17.so
bash    32629 root  mem    REG  253,1         657639 /usr/lib64/libtinfo.so.5.9
bash    32629 root  mem    REG  253,1         657554 /usr/lib64/ld-2.17.so
bash    32629 root  mem    REG  253,1         787497 /usr/lib64/gconv/gconv-modules.cache
bash    32629 root    0u   CHR  136,1    0t0       4 /dev/pts/1
bash    32629 root    1u   CHR  136,1    0t0       4 /dev/pts/1
bash    32629 root    2u   CHR  136,1    0t0       4 /dev/pts/1
bash    32629 root    8r   REG  253,1   0t18  137823 /root/newDir/newfile.txt
bash    32629 root  255u   CHR  136,1    0t0       4 /dev/pts/1

第二个进程

[root@LinuxOparation fd]# exec 6< /root/newDir/newfile.txt 
[root@LinuxOparation fd]# lsof -op $$
[root@LinuxOparation fd]# read a <& 6
[root@LinuxOparation fd]# echo $a
aa
[root@LinuxOparation fd]# lsof -op $$
COMMAND   PID USER   FD   TYPE DEVICE OFFSET    NODE NAME
bash    32479 root  cwd    DIR    0,3        2214612 /proc/32479/fd
bash    32479 root  rtd    DIR  253,1              2 /
bash    32479 root  txt    REG  253,1         657640 /usr/bin/bash
bash    32479 root  mem    REG  253,1         666054 /usr/lib/locale/locale-archive
bash    32479 root  mem    REG  253,1         663465 /usr/lib64/libnss_files-2.17.so
bash    32479 root  mem    REG  253,1         657568 /usr/lib64/libc-2.17.so
bash    32479 root  mem    REG  253,1         663461 /usr/lib64/libdl-2.17.so
bash    32479 root  mem    REG  253,1         657639 /usr/lib64/libtinfo.so.5.9
bash    32479 root  mem    REG  253,1         657554 /usr/lib64/ld-2.17.so
bash    32479 root  mem    REG  253,1         787497 /usr/lib64/gconv/gconv-modules.cache
bash    32479 root    0u   CHR  136,0    0t0       3 /dev/pts/0
bash    32479 root    1u   CHR  136,0    0t0       3 /dev/pts/0
bash    32479 root    2u   CHR  136,0    0t0       3 /dev/pts/0
bash    32479 root    6r   REG  253,1    0t3  137823 /root/newDir/newfile.txt
bash    32479 root  255u   CHR  136,0    0t0       3 /dev/pts/0

可以看到两个进程读取/root/newDir/newfile.txt文件的偏移量都不一致。